The current rapid growth in traffic demand in communication networks is expected to continue in the next few years. High capacity networks capable of efficiently handling voice, video, and data are necessary to satisfy the growing demand. The high bandwidth capacity of optical communication networks make such networks the most promising candidates to satisfy the expected demand.
The existing optical networks usually employ circuit switching technology, and are not suitable for data applications involving bursty traffic. The current approach to implement packet-switching technology in optical networks is to keep the data in the optical domain and convert the control signal to the electrical domain for signal processing. C. Qiao and Yoo M., “Optical burst switching (OBS)—a new paradigm for an optical Internet,” Journal of High Speed Networks, vol. 8, pp. 69-84 (1999), and Renaud M. et al., “Transparent optical packet switching: The European ACTS KEOPS project approach,” Proceedings of LEOS 99, vol. 2, pp. 401-402 (1999) describe examples of the two domain, or hybrid, approach and are herein incorporated by reference.
The hybrid approach is adequate for the present demand for high speed packet-switched networks and combines the flexibility of electronics and the huge transmission bandwidth of optics. The packet switching rate, however, is limited by the comparatively low bandwidth of electronic devices and as the transmission rate increases, the header processing overheads become significant.
All-optical packet-switched networks, hereinafter referred to as optical networks, keep both the data and control signals in the optical domain from the source node to the destination node. The optical domain is typically characterized by carrier frequencies greater than about 100 THz. Chan V. W. S. et al., “Architectures and technologies for high-speed optical data networks,” Journal of Lightwave Technology, vol. 16, no. 12, pp. 2146-2168 (1998) describes an example of an all-optical network and is herein incorporated by reference.
Optical networks, however, are presently limited by the lack of efficient buffers and relatively limited optical processing capabilities. The inventors describe in Yuan X. C., et al, “A novel self-routing scheme for all-optical packet switched networks with arbitrary topology,” Proceedings of ICC 2001, vol. 7, pp. 2155-2159 (2001), herein incorporated by reference, one method of bypassing the optical processing limitation of optical networks. In this method, the required signal processing in the node is significantly reduced by a self-routing scheme that can be implemented using bitwise optical logic gates only.
In packet-switched networks, a conflict arises when two or more packets request the same output link in a node. In store-and-forward routing, the node stores the conflicting packets temporarily in buffers so that all packets are optimally routed over the shortest path. Unlike electronic buffers, optical buffers are limited and inefficient. Optical buffers are usually made from fiber delay lines, which are bulky and have a fixed delay. Furthermore, optical logic devices are presently limited to simple Boolean logic functions such as AND, OR, NOR, INVERT, and XOR operations that are difficult to integrate thereby making complex optical logic circuits, required for store-and forward routing, prohibitively expensive.
Deflection routing allows one to avoid or reduce the use of buffers by intentionally routing the packets that lose in a conflict to the ‘wrong’ output ports. The misrouted packets will find their way to their destination nodes but their arrival will be delayed. Deflection routing, in effect, uses the network links as the temporary storage for the packets. Acampora A. S. and Shah S. I. A., “Multihop lightwave networks: A comparison of store-and-forward and hot-potato routing,” IEEE Transactions on Communications, vol. 40, no. 6, pp. 1082-1090 (1992), herein incorporated by reference, describes and compares store-and-forward routing to one method of deflection routing that bypasses the optical buffer limitation of optical networks. Deflection routing as described by Acampora and Shah, however, are not suitable for all-optical packet-switched networks because of the high demand of processing power at intermediate nodes.
In traditional deflection routing, a node determines the optimal paths from itself to the destination node. Packets requesting the same output port in a node are prioritized according to a deflection criterion, for example age or distance-to-destination. The packet with the higher priority is routed optimally to the shortest path while the conflicted packet having a lower priority is deflected to a link having a longer path length. In traditional deflection routing, a node must have the capability to determine the optimal paths of arriving packets and compare the deflection criteria of conflicting packets. The required optical processing capability required of each intermediate node is both complex and prohibitively expensive, making the implementation of such a deflection routing method uneconomic.
Therefore, there remains a need for providing a method for deflection routing that does not require large optical processing capabilities at the intermediate nodes.